The characterizing features of the sub-combat unit described in the above-mentioned patent are that the target detector is pivotally disposed on a journal shaft which is parallel to the line of symmetry of the warhead so as to permit outward pivoting of the target detector from a closed position where the optical axis of the target detector coincides with the line of symmetry of the warhead, and to in opened position where the optical axis of the target detector is parallel to the line of symmetry of the warhead so as to permit free view of the target detector beside the warhead, and that, an additional, carrier surface is pivotally disposed on a journal shaft which is also parallel to the line of symmetry of the warhead so as to permit outward pivoting of the carrier surface from a closed position to an opened position beside the warhead.
By a suitable aerodynamic design of the sub-combat unit and the retarding area of the detector and carrier surface, there will be obtained a suitable fall velocity of the sub-combat unit and further an impelling moment about the spinning axis which gives the sub-combat unit its rotation. This is achieved without the aid of a parachute, which is an advantage since the parachute is bulky and requires space. Within the available space in a carrier shell, more space can instead be made available for the warhead proper.
Even if the above-described sub-combat unit has proved to possess superior properties in respect of fall velocity and scanning rotation, wishes have been voiced in the art to be able to increase the retarding area even further. This may, for instance, be the case when it is desired to employ heavier warheads. The retarding area of the target detector and carrier surface is restricted to the cross-sectional area of the cylindrical sub-combat unit body, which may entail that the fall velocity will become too high with the existing size of the retarding area if, at the same time, the weight of the warhead is increased.
Swedish patent application number 8903474-8 corresponding to U.S. Pat. No. 5,088,414, describes a sub-combat unit in which the retarding area has been made considerably larger. The characterizing feature of the sub-combat unit is that two diametrically located carrier surfaces are pivotally disposed each on then shaft located in a plane which is at light angles to the axis of symmetry of the warhead, from a closed position where the carrier surfaces follow the casing surface of the sub-combat unit, to a 90 degrees opened position where both of the carrier surfaces form a retarding area for the fall velocity of the sub-combat unit.
In this case, the carrier surfaces are made of an elastically flexible material, so that, when they pivot out from then closed position, they are at the same time bent to a substantially straight oi gently curved surface.
The advantage inherent in the above-described design, in addition to the larger retarding area, is that both of the carrier surfaces may be made comparatively thin, which is favorable from the point of view of weight and payload. For example, the carrier surfaces may be made of titanium and bent so that, in then opened position, they have a certain radius. The bending may be varied and the carrier surfaces may be of different lengths, in which event further parameters for varying the aeronautical properties of the unit will be obtained.
The sub-combat units are disposed to be separated from a missile, a carrier shell or other flying platform, for example a canister which in its turn has been separated from a carrier shell or missile, for example a 15.5 cm artillery shell.
In order that the sub-combat unit in its functional phase (the scanning phase) operate in the intended manner, it is necessary that the axis of rotation is close to vertical and that the pendulum movements of the axes are slight, with an amplitude of at most a few degrees. By designing the two carrier surfaces with accurately indicated geometry and by providing them with means for completely relieved (turbulent) flow, see our copending patent application Ser. No. 07/957,487, filed Oct. 7, 1992, pendulum motion and instabilities can be reduced to a minimum and a predetermined rotation, fall velocity and orientation can be maintained during the scanning phase.
When the sub-combat units are fast separated from the shell and subsequently from the canister, the flying state of the sub-combat units is, however, highly varied, depending upon discharge descent, different from the described state, i.e. a state in which the axis of rotation is near to vertical as is to apply during the scanning phase.
In most cases, the carrier (for example an artillery shell, missile or canister) will, on discharge of the sub-combat units, have a trajectory which may be as good as horizontal. On discharge, the sub-combat unit will begin to rotate about its major main inertia axis, at the same time as this axis will begin to oscillate. The major direction of the axis will, however, be largely parallel to the trajectory tangent of the carrier prior to separation.